The present invention relates to a method of processing seismic data to obtain a processed seismic data volume. The seismic data is a quantity, for example the magnitude of the seismic amplitude, assigned to voxels in a seismic data volume that represents a pre-determined volume of earth. A voxel is a small volume elementxe2x80x94the three-dimensional equivalent of a pixel. The seismic data is assigned to the center of the voxel.
Seismic images play an important role in the study of underground formations, and in particular in the study of underground formations that contain hydrocarbons. In particular in the latter field it is of great importance to be able to identify structural and stratigraphic features in order to detect faults, which are discontinuities in the reflectors.
Therefore there is a great interest in techniques that allow noise reduction and preservation of faults, in particular there is great interest in a technique that takes into account the characteristics of the underground reflectors.
It is an object of the present invention to suppress (incoherent) noise in the seismic image without affecting the structural information in the image. The structural information is contained in the reflectors and in the faults.
To this end the method of processing seismic data to obtain a processed seismic data volume according to the present invention comprises the steps of:
a) obtaining seismic data covering a pre-determined volume of earth, which seismic data comprises a quantity assigned to a voxel in a seismic data volume that represents the pre-determined volume of earth;
b) determining for each voxel in the seismic data volume a local orientation of the seismic data, which local orientation is the orientation of a plane tangent to the seismic data in that voxel;
c) determining for each voxel whether there is an edge in its neighborhood; and
d) carrying out a smoothing operation on each voxel in the seismic data volume, in a direction such that the direction of the smoothing operation is the local orientation of the data and wherein the smoothing operation does not go over the edge, to obtain a processed seismic data volume in which the quantity assigned to each voxel in the processed data volume is a result obtained by carrying out the smoothing operation in that voxel in the seismic data volume.